Action cameras like for example actioncams from GoPro typically have an incorporated microphone. The action cameras are optionally provided with a water-tight reverberant case. As a result the quality of audio recording under that case by the incorporated microphone is however poor.
DE 197 15 365 C2 discloses a condenser microphone having a microphone housing and a first diaphragm and a second diaphragm which is provided in the form of a passive freely oscillating sealing diaphragm. If however such microphones are immersed in water it often happens that drops of water remain on the speaking hole and thus close off the speaking hole.
In the German patent application from which priority is claimed the German Patent and Trade Mark Office searched the following state of the art: JP 4456656 B1, US 2006/140432 A1, JP H07245794 A, US 2016/234594 A1, WO 2006/128956 A1, DE 197 15 365 A1, US 2014/211974 A1, US 2010/111345 A1 and DE 2 545 993 A1.